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- 1. Appl. Phys. Lett. 90, 013104 (2007) , “Scanning tunneling microscopy investigations of hydrogen plasma-induced electron scattering centers on single-walled carbon nanotubes”, G. Buchs, P. Ruffieux, P. Gröning, and O. GröningThe authors report on the generation of localized defects on single-walled carbon nanotubes by means of a hydrogen electron cyclotron resonance plasma. The defects have been investigated using scanning tunneling microscopy (STM) and show an apparent topographic height in the STM of 1–3 ... (Read more)
- 2. Phys. Rev. B 75, 195335 (2007) , “Computational and experimental imaging of Mn defects on GaAs (110) cross-sectional surfaces”, A. Stroppa, X. Duan, M. Peressi, D. Furlanetto, and S. ModestiWe present a combined experimental and computational study of the (110) cross-sectional surface of Mn δ-doped GaAs samples. We focus our study on three different selected Mn defect configurations not previously studied in detail, namely surface interstitial Mn, isolated and in pairs, and... (Read more)
- 3. Phys. Rev. B 75, 195209 (2007) , “Mechanism and energetics of self-interstitial formation and diffusion in silicon”, Ramakrishnan Vaidyanathan, Michael Y. L. Jung, and Edmund G. SeebauerRecent work has suggested that prior determinations of diffusion mechanism and point defect thermodynamics in silicon have been affected by nonequilibrium effects stemming from uncontrolled adsorption-induced suppression of a pathway for defect creation at the surface. Through silicon self-diffusion... (Read more)
- 4. Phys. Rev. B 75, 193409 (2007) , “Magnetic properties of vacancies in a graphitic boron nitride sheet by first-principles pseudopotential calculations”, M. S. Si and D. S. XueWe use ab initio methods to calculate the magnetic properties of vacancies in a graphitic boron nitride sheet (g-BN). By applying a full spin-polarized description to the system, we demonstrate that the nitrogen vacancy (VN) or the boron vacancy (VB)... (Read more)
- 5. Phys. Rev. B 75, 115418 (2007) , “Early stages of radiation damage in graphite and carbon nanostructures: A first-principles molecular dynamics study”, Oleg V. Yazyev, Ivano Tavernelli, Ursula Rothlisberger, and Lothar HelmUnderstanding radiation-induced defect formation in carbon materials is crucial for nuclear technology and for the manufacturing of nanostructures with desired properties. Using first-principles molecular dynamics, we perform a systematic study of the nonequilibrium processes of radiation damage in... (Read more)
- 6. Phys. Rev. B 75, 085439 (2007) , “Real-space investigation of fast diffusion of hydrogen on Si(001) by a combination of nanosecond laser heating and STM”, C. H. Schwalb, M. Lawrenz, M. Dürr,, and U. HöferThe rearrangement of silicon dangling bonds induced by pulsed laser heating of monohydride-covered Si(001) surfaces has been studied by means of scanning tunneling microscopy (STM). The initial configurations, which were created by laser-induced thermal desorption, consist of isolated pairs of... (Read more)
- 7. Phys. Rev. B 75, 085423 (2007) , “Room-temperature atmospheric oxidation of Si nanocrystals after HF etching”, X. D. Pi, L. Mangolini, S. A. Campbell, and U. KortshagenThe effect of HF etching of the silicon oxide shell covering the surface of Si nanocrystals (NCs) on the subsequent room-temperature atmospheric oxidation of Si-NCs has been investigated by means of photoluminescence measurements, Fourier transform infrared spectroscopy, and electron paramagnetic... (Read more)
- 8. Phys. Rev. B 75, 085301 (2007) , “Electron backscatter diffraction and electron channeling contrast imaging of tilt and dislocations in nitride thin films”, C. Trager-Cowan, F. Sweeney, P. W. Trimby, A. P. Day, A. Gholinia, N.-H. Schmidt, P. J. Parbrook, A. J. Wilkinson, and I. M. WatsonIn this paper we describe the use of electron backscatter diffraction (EBSD) mapping and electron channeling contrast imaging—in the scanning electron microscope—to study tilt, atomic steps and dislocations in epitaxial GaN thin films. We show results from a series of GaN thin films of... (Read more)
- 9. Phys. Rev. B 75, 075420 (2007) , “Ab initio study of hydrogen interaction with pure and nitrogen-doped carbon nanotubes”, Zhiyong Zhang and Kyeongjae ChoDetailed studies of mechanisms for hydrogen dissociative adsorption and diffusion on pure and nitrogen-doped (8, 0) carbon nanotubes are carried out using the first-principles density functional theory method. (1) For pure carbon nanotubes, we have identified the energetically most favorable... (Read more)
- 10. Phys. Rev. B 75, 073409 (2007) , “Why thermal H2 molecules adsorb on SiC(001)-c(4×2) and not on SiC(001)-(3×2) at room temperature”, Xiangyang Peng, Peter Krüger, and Johannes PollmannIn a recent experiment, Derycke et al. have made the exciting observation that H2 molecules readily adsorb dissociatively on the c(4×2) but not on the 3×2 surface of SiC(001) at room temperature. To unravel this spectacular reactivity difference, we have investigated a... (Read more)
- 11. Phys. Rev. B 75, 024109 (2007) , “Optical and EPR properties of point defects at a crystalline silica surface: Ab initio embedded-cluster calculations”, L. Giordano, P. V. Sushko, G. Pacchioni, and A. L. ShlugerWe have studied the structure and spectroscopic properties of the paramagnetic nonbridging oxygen hole center and of the Egamma[prime]" align="middle"> center at the hydroxylated silica surfaces using density functional theory and an embedded-cluster model. To investigate the... (Read more)
- 12. Phys. Rev. Lett. 98, 075503 (2007) , “Pseudoclimb and Dislocation Dynamics in Superplastic Nanotubes”, Feng Ding, Kun Jiao, Mingqi Wu, and Boris I. YakobsonPlastic relaxation of carbon nanotubes under tension and at high temperature is described in terms of dislocation theory and with atomistic computer simulations. It is shown how the glide of pentagon-heptagon defects and a particular type of their pseudoclimb, with the atoms directly breaking out of... (Read more)
- 13. Phys. Rev. Lett. 98, 026802 (2007) , “Microscopic Basis for the Mechanism of Carrier Dynamics in an Operating p-n Junction Examined by Using Light-Modulated Scanning Tunneling Spectroscopy”, Shoji Yoshida, Yuya Kanitani, Ryuji Oshima, Yoshitaka Okada, Osamu Takeuchi, and Hidemi ShigekawaThe doping characteristics and carrier transport in a GaAs p-n junction were visualized with a ~10 nm spatial resolution, using light-modulated scanning tunneling spectroscopy. The dynamics of minority carriers under operating conditions, such as recombination, diffusion, and electric... (Read more)
- 14. Phys. Rev. Lett. 98, 026801 (2007) , “Surface Dangling-Bond States and Band Lineups in Hydrogen-Terminated Si, Ge, and Ge/Si Nanowires”, R. Kagimura, R. W. Nunes, and H. ChachamWe report an ab initio study of the electronic properties of surface dangling-bond (SDB) states in hydrogen-terminated Si and Ge nanowires with diameters between 1 and 2 nm, Ge/Si nanowire heterostructures, and Si and Ge (111) surfaces. We find that the charge transition levels ε(+/-)... (Read more)
- 15. Appl. Phys. Lett. 89, 243101 (2006) , “Random telegraph signals and noise behaviors in carbon nanotube transistors”, Fei Liu, Kang L. Wang, Daihua Zhang, and Chongwu ZhouA random telegraph signal appears at a smaller absolute gate bias for a larger absolute drain-source bias in a carbon nanotube transistor. Its mechanism is attributed to a defect located in the drain side of the Schottky barrier carbon nanotube transistor with Ti/Au as contact material. Furthermore,... (Read more)
- 16. Appl. Phys. Lett. 89, 231901 (2006) , “Cathodoluminescence investigations of GaInNAs on GaAs(111)B”, J. Miguel-Sánchez, U. Jahn, A. Guzmán, and E. MuñozIn this work, we present a detailed cathodoluminescence characterization of GaInNAs quantum wells grown on GaAs(111)B. As-grown and annealed InGaAs and GaInNAs quantum wells were maeasured and compared by spatially resolved cathodoluminescence at different photon energies. In the case of... (Read more)
- 17. Appl. Phys. Lett. 89, 222101 (2006) , “Reversible creation and annihilation of a local leakage path in HfO2/GeOx stacked gate dielectrics: A direct observation by ultrahigh vacuum conducting atomic force microscopy”, K. Yamamura, K. Kita, A. Toriumi, and K. KyunoBy direct observation using ultrahigh vacuum conducting atomic force microscopy, it is found that a local leakage path in HfO2/GeOx stacks created by an electrical stress with a positive tip bias annihilates after applying a reverse tip bias. The creation and... (Read more)
- 18. Appl. Phys. Lett. 89, 041916 (2006) , “Photoluminescence evaluation of defects generated during SiGe-on-insulator virtual substrate fabrication: Temperature ramping process”, Dong Wang, Seiichiro Ii, Hiroshi Nakashima, Ken-ichi Ikeda, Hideharu Nakashima, Koji Matsumoto, and Masahiko NakamaeCrystal qualities of Si/SiGe/Si-on-insulator structures with different SiGe thicknesses were evaluated by photoluminescence (PL). The wafers were annealed at different temperatures with a ramping rate of 5 °C/min. Free exciton PL peaks were clearly observed for the as-grown wafers and decreased... (Read more)
- 19. J. Appl. Phys. 99, 113520 (2006) , “Effects of hydrogen bond redistribution on photoluminescence of a-SiC:H films under thermal treatment”, A. V. Vasin, S. P. Kolesnik, A. A. Konchits, V. I. Kushnirenko, V. S. Lysenko, A. N. Nazarov, A. V. Rusavsky, and S. AshokHydrogenated amorphous silicon carbide (a-SiC:H) films have been deposited using magnetron sputtering technique. An integrated investigation of the effect of vacuum annealing temperature on photoluminescence properties and paramagnetic defects and its correlation with structural... (Read more)
- 20. J. Appl. Phys. 99, 023523 (2006) , “Characterization of 6H-SiC surfaces after ion implantation and annealing using positron annihilation spectroscopy and atomic force microscopy”, G. Brauer, W. Anwand, W. Skorupa, S. Brandstetter, and C. TeichertSystematic slow positron implantation spectroscopy (SPIS) and atomic force microscopy studies of various 6H-SiC samples are presented to clarify the role of conductivity type, crystal quality, ion implantation (B+,Al+, and N+), and annealing (1.650 °C) in... (Read more)
- 21. Nature 442, 436 (2006) , “Atom-by-atom substitution of Mn in GaAs and visualization of their hole-mediated interactions”, D. Kitchen, A. Richardella, J. -M. Tang, M. E. Flatt, A. YazdaniThe discovery of ferromagnetism in Mn-doped GaAs1 has ignited interest in the development of semiconductor technologies based on electron spin and has led to several proof-of-concept spintronic devices2, 3, 4. A major hurdle for realistic applications of Ga1-XMnXAs, or other dilute magnetic semiconductors, remains that their ferromagnetic transition temperature is below room temperature. Enhancing ferromagnetism in semiconductors requires us to understand the mechanisms for interaction between magnetic dopants, such as Mn, and identify the circumstances in which ferromagnetic interactions are maximized5. Here we describe an atom-by-atom substitution technique using a scanning tunnelling microscope (STM) and apply it to perform a controlled study at the atomic scale of the interactions between isolated Mn acceptors, which are mediated by holes in GaAs. High-resolution STM measurements are used to visualize the GaAs electronic states that participate in the Mn–Mn interaction and to quantify the interaction strengths as a function of relative position and orientation. Our experimental findings, which can be explained using tight-binding model calculations, reveal a strong dependence of ferromagnetic interaction on crystallographic orientation. This anisotropic interaction can potentially be exploited by growing oriented Ga1-XMnXAs structures to enhance the ferromagnetic transition temperature beyond that achieved in randomly doped samples. (Read more)
- 22. Phys. Rev. B 74, 245411 (2006) , “Vacancy defects and the formation of local haeckelite structures in graphene from tight-binding molecular dynamics”, Gun-Do Lee, C. Z. Wang, Euijoon Yoon, Nong-Moon Hwang, and K. M. HoThe dynamics of multivacancy defects in a graphene layer is investigated by tight-binding molecular dynamics simulations and by first principles calculation. The simulations show that four single vacancies in the graphene layer first coalesce into two double vacancies, each consisting of a... (Read more)
- 23. Phys. Rev. B 74, 235426 (2006) , “First-principles study of electronic properties of hydrogenated graphite”, A. Allouche and Y. FerroProgressive implantation of hydrogen atoms into graphite is modeled by first-principles density functional theory. The maximum H/C ratio was found at 53%, which is in good agreement with experimental results. The hydrogen trapping energy varies from −0.7 eV at very low concentrations to a... (Read more)
- 24. Phys. Rev. B 74, 235301 (2006) , “Precursor mechanism for interaction of bulk interstitial atoms with Si(100)”, Xiao Zhang, Min Yu, Charlotte T. M. Kwok, Ramakrishnan Vaidyanathan, Richard D. Braatz, and Edmund G. SeebauerIn the same way that gases react with surfaces from above, solid-state point defects such as interstitial atoms can react from below. Little attention has been paid to this form of surface chemistry. Recent bulk self-diffusion measurements near the Si(100) surface have quantified Si interstitial... (Read more)
- 25. Phys. Rev. B 74, 205324 (2006) , “Surface smoothness of plasma-deposited amorphous silicon thin films: Surface diffusion of radical precursors and mechanism of Si incorporation”, Mayur S. Valipa, Tamas Bakos, and Dimitrios MaroudasWe present a detailed analysis of the fundamental atomic-scale processes that determine the surface smoothness of hydrogenated amorphous silicon (a-Si:H) thin films. The analysis is based on a synergistic combination of molecular-dynamics (MD) simulations of radical precursor migration on surfaces... (Read more)
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